A low-noise charge sensitive amplifier for MEMS capacitive sensors

This paper describes a low-noise charge sensitive amplifier (CSA) for MEMS capacitive sensors which uses a chopper technique to reduce the low-frequency noise and offset. The feedback resistors of the CSA are implemented as a MOS-bipolar pseudo-resistors and an input common-feedback (ICMFB) is designed to prevent large output errors from input common-shift and maintain the op-amp within its input common-mode range. A simulated resolution of 5.8aF (rms) in capacitive change integrated over the signal band is achieved while chopped at 1 MHz. ? 2006 IEEE.EI